1. Field of the Invention
The present invention relates to a pressure sensor, and more particularly to a pressure sensor for use as a knock sensor for an internal combustion engine and which operates on the piezoelectric principle.
2. Description of the Prior Art
In the prior art, pressure sensors used as knock sensors in internal combustion engines are known which are attached in such a manner to the internal combustion engine that they indicate the momentarily-prevailing pressure within a cylinder. For the sake of complete completeness, such knock sensors are attached to the exterior wall of the engine block.
In FIG. 1, a crystal pressure transducer, having short-time temperature compensation, is illustrated, such as the type 12 QP 505 cl. This pressure transducer is to be screwed into the engine block with the threads 1 so that a plate 2 is positioned within a cylinder and is exposed to the prevailing pressure relationships within the cylinder. Short feed conduits for coolant are provided, as at 3 and 4. Such pressure transducers are so expensive that the use thereof is only considered in connection with diagnostic equipment.